Underwater noise is a severe annoyance and danger to marine life. The innovative Hydro Sound Dampers (HSD) lead to an effective general method to reduce piling underwater noise. HSD were developed between 2007 and 2010 by K.-H. Elmer to reduce marine and offshore piling noise. The theory and the acoustical background of the new noise mitigation method will be presented.
HSD systems use nets with air filled elastic balloons and special PE-foam elements with high dissipative effects to reduce continuous and impact noise. The resonance frequency of the HSD-elements, the optimum damping rate for impact noise, the distribution and the effective frequency range can be fully controlled. Offshore tests and serial applications in offshore wind farms in Germany and Great Britain demonstrate this new effective way to reduce the very high offshore piling noise. It is also intended to use systems of Hydro Sound Dampers in Australia to reduce high underwater piling noise levels in coastal ports and harbours. HSD-systems are very small systems and easy to handle. They are more effective than air-bubble curtains, independent of compressed air, not influenced by tidal currents, not expensive and easy adaptable to different applications.
Measured results of underwater noise reductions between 10dB (SEL) and more than 20dB (SEL) will be presented and discussed.